Particle image velocimetry analysis of IC engine in-cylinder flows

This paper discusses the use of particle image velocimetry for measuring in-cylinder flows in multi-valve IC engines. The techniques and their limitations are discussed with special reference to the study of large-scale flow structures in a four valve optical IC engine exhibiting significant barrel swirl. Examples of velocity vector maps derived by digital autocorrelation are presented for a range of crank angles through the induction and compression strokes from both horizontal and vertical measurement planes. The evident strengths and limitations of the current technique for in-cylinder applications are discussed with respect to spatial resolution, velocity gradients and dynamic range. Recent developments for overcoming the limitations are also reviewed.